Process for making isobutylene polymers of high molecular weight



Oct. 17, 1939. 1.. A. BANNON PROCESS FOR BAKING ISOBUTYLENE POLYMERS OF HIGH IOLECULAR WEIGHT Filed NOV. 21, 1936 GAS LINE r/Ic In 1. (Ni

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PATENT oi-"Flea smarts rnocsss roams rsonu'rrnm m.

ms or men uonscouia wsron'r Louis ard Oil of Delaware dilannomltosellamlsassignorto Stand- Devciopment company, a corporation Application November :1: 1m, Serial No. 11am '10 Claims.

The present invention relates to theproduction of extremely heavy polymers from lsobutylene.

pure isobutylene is subjected to the action-oi fluoride at a sub-serotemperature, it polymerlaes very rapidly to hydrocarbons of high molecular weight, ranging upwardly from 5000 and varying in physical nature from a viscous oil to a tough rubberlike solid. In its highly polymerized state. the polymer has a molecular weight in the neighborhood of 200,000.

In carrying out this process, isobutylene in the liquid state, is fed with a liquid refrigerant, such aaethylene, ethane. propylene propane, etc.. into a reactionjsone into which boron fluoride is in- The heat of reaction vaporizes the refrigerant which of! overhead together with some of the boron fluoride. The refrigerant isthen conducted to a water scrubbing tower, the purpose of which is to hydrolyze any boron fluoride present, next through acid scrubbing towers in which the gas is scrubbed withconcentrated sulfuric acid for the purpose of removing unconvertedisobutylene, and then through a drum of flake caustic for removing any entrained acidity and is then compressed. Upon compression, it is again treated to make certain that residual acidity and moisture are removed, and it is then cooled to the liquid state, after which it is mixed with isobutylene and introduced into the reaction chamber.

In-the operation, of this process, it has frequently been found that, for some inexplicable reason, a polymer of satisfactory molecular weight could not be obtained consistently, although operating conditions were carefully controlled and the recycle gas was carefully purified in the manner described above. In some instances, the polymer would reach only a certain molecular weight very much below that desired and the reaction would then cease or, if the reaction proceeded, the product would be sticky.

It has now been found that the reason for the aforesaid difllculty is that the diluent gas, which in the present case is also the refrigerant, in leaving the reaction chamber carries with it some isobutylene which is in part polymerized by the action of the boron fluoride carried 06 from the reaction before the diluent gas reaches the suliuricacid. It is also possible thatin the treatment with sulfuric acid to remove isobutylene some of the latter is converted into dimer and trimer which are not soluble in the acid. In any case, small traces of polymers are carried through the system by the diluent gas and back into the reaction chamber. These low molecular weight polymers act as poisons to the polymerization of isohutylene to high molecular weight polymers and prevent the polymerization from progressing to the desired extent.

In order to overcome this dlfliculty, it is proposed, according to the present invention. to sub- Ject the diluent gas to a treatment for the removal of these low molecular weight polymers such as to the action of an absorbent material, Just prior to its re-introductiodinto the reaction chamber. For this purpose, the diluent gas, after the other various purifying treatments and, at any rate, after the treatment with concentrated sulfuric acid, is contacted with active carbon, highlyabsorbent clay or any other suitable absorbent packed in a tower. The inclusion of this step in the process results in the production of a more uniform product of higher average molecular weight than is attainable when this step is omitted. l

A front elevation of an apparatus suitable for carrying out the process of the present invention is illustrated in diagrammatic form in the attached drawing, in which I is a reaction chamber, which is usually heavily heat insulated, and provided with a removable cover I, the operation tobe described being a batch operation. Chamber I is provided with inlet 3 for the diluent, (which in the present case also acts as the refrigerant and is ethylene and isobutylene), inlet 1 for boron fluoride, and with an exhaust pipe 6 for the elimination of vaporized diluent and boron fluoride.

The diluent containing boron fluoride and some isobutylene is conductedby pipe 5 to a scrubbing tower 8 which is packed with contact material, such as glass or porcelain balls, Raschig rings. or the like. in the usual manner, or provided with internal equipment, such as discs and doughnuts. This tower has a water inlet I at its top and an outlet I for the scrubbed gases. In this tower, the boron fluoride is hydrolyzed and boric hydroxide collects at the bottom of the tower and may be withdrawn from time to time in any suitable manner.

The diluent, still containingg'isobutylene, is then conducted by line 8 to one or ore acid scrubbing towers 9, which are similar the water scrubhing tower with the exception of course that they are provided at the top with inlets for acid which is carried in line III. In these towers the isobutylene is absorbed.

The diluent gas is then conducted by line H from the acid scrubbing towers to a drum I! filled with flake caustic which serves to eliminate any entrained acid in the diluent. The thus purified diluent is then passed through line it and compressor ll to a storage tank i5 from which it is withdrawn when needed through line it and passed, if necessary, through another tower I! which is packed partially with flake caustic and partially with calcium chloride. This second treatment with flake caustic can ordinarily be pensed with, and is only included as an e ordinary safeguard against the possibility of a acidbeing carriedbythe diluentbachtothereaction chamber. rdina1iiy,-iiahe caustic in this sone functions more as a dehydrating agent than as a neutralising agent.

The diluent is then passed through line in thebottomoitower-llwhichispackedwitha solid absorbent in accordance with theflpresent invention. Leaving tower II at its top through line II, the diluent passesthrough cooling coil II which is surrounded by a chamber}! which may be iiiiedwith any-suitable refrigerating medium.

' With ethylene as the diluent, a suitable refrig- Consecutive runs' Consecutive runs be- A with use 0! ohm lore use oi charcoal and Run No. M. W. Run No. M. W.

i2 135, (I30 22 i8), 000 13 42, 23 100,000 14 118, 1m 24 180.0(1) i2 1% t cs 17 132, 27 I88, 000 i8 125. 000 2B 140, D0 130. GI] 20 153, ill) 2) 135, (Ill M) 150, [D0 21 02,

As can be seen irom the above tables, the use '01 the adsorbent in the purification of the diluent led to the production of a product which was uniiormly of higher molecular weight than the prodnot obtained when the adsorbing step was omitted. In order to determine-exactly what was removed by the charcoal, the charcoal tower containing 354 cu. inches of charcoal, which was used in the production oi approximately 320 lb. of high molecular weight polymer, was steamed, and yielded 170 cc. 0! water insoluble material having a specific gravity of 0.7212, and having the m1- lowing boiling range:

Initial B. P. 103' C.

' 105 C." 7.0% C 9.0% C 25.0 C 43.0 C 61.5 C 86.0% C 88.0 C 93.0 Recovery 96.0% Loss- 3.0% I". B. P 167.BC

These characteristics indicate that the normally liquid impurities removed from the circulated diluent were composed of dimer and triiner of isobutylene. It follows that it was the introduction of these substances into the reaction chamber which caused the previous diihculty in consistently obtaining polymers of the desired molecular weight.

In order to definitely establish the correctness o! the conclusion indicated by the above experiments,anumberoi'runsweremadeinwhich diicsbutyiene was purposely added-to the feed stock. In operating under conditions suitable for the promotions! a polymer having a molecular weight or 81,000, the addition oi 5% oi.

diisobutyiene to the reed reduced the molecular weight oi the polymer produced to 20,000, 1% oi diieobutylene reduced the molecular weight of the P er to about 10,500 and 3% of diisobutylene reduced the molecular weight polymer to 11,000.

It is apparent from the above description that the essence o! the present invention is the inclusion in the purification of a circulated diluent employed in the process oi producing polymers oi high-molecular weight from isobutylene of a treatment for the removal oi low molecular weight polymers. While this treatment has been described in the foregoing as an adsorption. it is apparent that it can be acontrolled chilling to a point above the liquefaction point of the diluent but considerably below the'boillng point oi the low molecular weight polymers, preferably followed by passage 01 the diluentthrough any absorption medium, such as asbestos or the like. In addition, this removal may be accomplished by scrubbing the gases with a liquid saturated hydrocarbon, such asbutane. pentane, etc.

Itisimmaterlaltothescopeotthepresent invention whether or not the diluent is also employed as the refrigerating medium. It is likewise unimportant insoiar as the present invention is concerned, what other purification steps are included in the treatment of the circulated diluent. Changes in these respects and other changes apparent to those skilled in the art are contemplated by the present invention, the scope oiwhichis defined by the llowing claims in which it is intended to claim e present invention as broadly as the prior art will permit.

I claim:

1. In the production of a high molecular weight polymer of isobutylene by p lymerizing isobupresence of an inert volatile diluent and low polymers of the type of dimer and trimer, separating the diluent from the high molecular weight polymer and recycling the diluent to the reaction chamber, the step oi removing the recycled diluent the low molecular weight polymers of isobutylene prior to its reintroduction into the reaction chamber.

2. In the production of a high molecularweight polymer of isobutylene by polymerizing isobu tylene by the action of boron fluoride in the presence of an inert diluent, separating the diluent from the polymer, subjecting the diluent to a purifying treatment including a scrubbing with sulphuric-acid and recycling the diluent to the reaction chamber, the step oi subjecting the diluent subsequent to its treatment with suloi' the phurlc acid to a treatment suitable for the removal therefrom oi! low molecular weight polymers of isobutylene prior to its reintroduction into the reaction chamber.

to the reaction chamber, step of contacting the 1 diluent with a solid adsorbent material prior to its reintroduction into the reaction chamber.

5. A process according to the preceding claim in which the solid adsorbent material is adsorbent carbon.

6. A process according to claim 2, in which the removal of low molecular weight polymers from the diluent gas is efiected by contacting said gas with a solid adsorbent material.

7. The process of producing a high molecular weight polymer of isobutylene comprising the steps of mixing isobutylene, boron fluoride and an inert diluent, polymerizing the mixture at a low temperature, separating the diluent, separating boron fluoride from the diluent, removing from the diluent partially polymerized isobutylene and remixing the diluent with boron fluoride and isobutylene for further polymerization at low temperature.

8. The process of producing a high molecular weight polymer of isobutylene, comprising the steps of polymerizing the isobutylene by the action of boron fluoride in the presence of an inert hydrocarbon more volatile than isobutylene, separating the diluent and volatile materials from the polymer, washing the diluent and volatile products with water, scrubbing with sulfuric acid, thereafter removing partially polymerized isobutylene from the diluent and returning same to the reaction zone with further isobutylene and boron fluoride.

9. In a process for polymerization of isobutylene to high molecular weight in presence of a volatile inert dfluent, the steps of removing partially polymerized isobutylene from the diluent and thereafter recycling the diluent for further polymerization use.

10. The process of producing high molecular weight polymers of isobutylene, comprising the steps of mixing isobutylene with boron fluoride in the presence of a volatile hydrocarbon refrigerant-diluent, polymerizing the isobutylene in the presence of the refrigerant-diluent vaporizing the diluent along with more volatile materials and separating it from the polymer, washing the vaporized diluent with water and with acid, reducing the amount of polymerized isobutylene to mere traces and then mixing the reirigerant-diluent with further quantities of isobutylene and boron fluoride and polymerizing the further quantities of isobutylene in the presence of the washed diluent.

LEWIS A. BANNON.

CERTIFICATE OF C0 RRECTI ON;

Patent No 2,17 6,19Li.

October 17, 19 59.

IEWIS A.BANNON.

It is hereby certified that error appears in the above'numbered patent requiring correction as follows: In the grant, line 1b,, name oi assignee, for "Standard Oil Develoment Company" read Standard Oil Development Company as shown by the record of assignments in this office; page 2, second column, lines 5 and L 6 claim 1, strike out the words "and low polymers of the type of dimer and trimer" and insert the sameafter "diluent" in l n 1L7, same claim; line 1 ,9, same claim 1, after "removing" insert from;

and that the said Letters Patent ehouldbe readwith this correction therein that the samernay conform to the recorder the case in the Patent office.

Signed and sealed this 2nd day or January, A. D. 19!;0.

Henry Van Arsdale, Acting Commissioner of Patents.

diluent with a solid adsorbent material prior to its reintroduction into the reaction chamber.

5. A process according to the preceding claim in which the solid adsorbent material is adsorbent carbon.

6. A process according to claim 2, in which the removal of low molecular weight polymers from the diluent gas is efiected by contacting said gas with a solid adsorbent material.

7. The process of producing a high molecular weight polymer of isobutylene comprising the steps of mixing isobutylene, boron fluoride and an inert diluent, polymerizing the mixture at a low temperature, separating the diluent, separating boron fluoride from the diluent, removing from the diluent partially polymerized isobutylene and remixing the diluent with boron fluoride and isobutylene for further polymerization at low temperature.

8. The process of producing a high molecular weight polymer of isobutylene, comprising the steps of polymerizing the isobutylene by the action of boron fluoride in the presence of an inert hydrocarbon more volatile than isobutylene, separating the diluent and volatile materials from the polymer, washing the diluent and volatile products with water, scrubbing with sulfuric acid, thereafter removing partially polymerized isobutylene from the diluent and returning same to the reaction zone with further isobutylene and boron fluoride.

9. In a process for polymerization of isobutylene to high molecular weight in presence of a volatile inert dfluent, the steps of removing partially polymerized isobutylene from the diluent and thereafter recycling the diluent for further polymerization use.

10. The process of producing high molecular weight polymers of isobutylene, comprising the steps of mixing isobutylene with boron fluoride in the presence of a volatile hydrocarbon refrigerant-diluent, polymerizing the isobutylene in the presence of the refrigerant-diluent vaporizing the diluent along with more volatile materials and separating it from the polymer, washing the vaporized diluent with water and with acid, reducing the amount of polymerized isobutylene to mere traces and then mixing the reirigerant-diluent with further quantities of isobutylene and boron fluoride and polymerizing the further quantities of isobutylene in the presence of the washed diluent.

LEWIS A. BANNON.

CERTIFICATE OF C0 RRECTI ON;

Patent No 2,17 6,19Li.

October 17, 19 59.

IEWIS A.BANNON.

It is hereby certified that error appears in the above'numbered patent requiring correction as follows: In the grant, line 1b,, name oi assignee, for "Standard Oil Develoment Company" read Standard Oil Development Company as shown by the record of assignments in this office; page 2, second column, lines 5 and L 6 claim 1, strike out the words "and low polymers of the type of dimer and trimer" and insert the sameafter "diluent" in l n 1L7, same claim; line 1 ,9, same claim 1, after "removing" insert from;

and that the said Letters Patent ehouldbe readwith this correction therein that the samernay conform to the recorder the case in the Patent office.

Signed and sealed this 2nd day or January, A. D. 19!;0.

Henry Van Arsdale, Acting Commissioner of Patents. 

